Hypertension describes a symptom of several disease entities, both of known and unknown etiology, blood pressure being one measurement indicating its presence. There are two components of blood pressure, the systolic, which is the pressure produced by the pumping action of the heart and which has a normal measurement of between 120 and 140 ml. of mercury, and the diastolic pressure, which is the pressure due to the peripheral resistance of the blood vessels, normally having a value between 70 and 90 ml. of mercury. The systolic pressure is much more apt to be labile, varying with emotion and stress while the diastolic pressure is commonly more stable. A persistently elevated diastolic pressure is considered a serious symptom. Normal blood pressure varies with individuals, circumstances, and techniques used for measurement. Normal values also tend to rise during an individual's life time. High blood pressure can be temporary or can result from known causes such as kidney or artery disease. While some types of hypertension respond only to surgery and in others sedatives may comprise the sole therapy, most forms of hypertension are treated by means of chemotherapy. Chemical entities capable of lowering blood pressure in mammals are consequently highly desirable.